The present invention relates to a slip ring mechanism adapted for use in extreme conditions, for example, space and a vacuum.
Generally, spacecraft, such as an artificial satellite, is equipped with various space apparatuses, for example, an antenna apparatus including a rotary driving portion. Such an apparatus on spacecraft includes a well-known slip ring mechanism as means for transmitting or receiving a signal including power to or from the rotary portion. In the slip ring mechanism, a rotor having slip rings is coaxially attached to the rotation axis of a rotary portion. A stator having brushes is attached to a fixture support. When the rotor is rotated in accordance with the rotation of the rotary portion, the brushes of the stator are slid on the slip rings of the rotor. As a result, a signal is transmitted between the rotor and the stator.
When the aforementioned slip ring mechanism is used in space of a very high temperature and vacuum, it is difficult to use oil or grease as a lubricant as is used on the ground.
There are two types in slip ring mechanisms for use in space: one is sliding type, and the other non-sliding type. In the case of a slip ring mechanism of sliding type, the slip rings and brushes are made of self-lubricant material, such as gold or silver, to transmit signals between the rotor and the stator. In the case of a slip ring mechanism of non-sliding type, conductive fluid, e.g., mercury, is interposed between the slip rings and the brushes, so that the slip rings may not directly slide on the brushes. In this state, signals are transmitted between the rotor and the stator.
However, the slip ring mechanism of sliding type has the following drawbacks. The lifetime of this type is short, because the rings or brushes are liable to wear and the electric performance is easily lowered due to its structure.
In the slip ring mechanism of non-sliding type, the structure of arrangement of the conductive fluid is very complicated. Moreover, since it is difficult to completely prevent the fluid from leakage, the mechanism has only low reliability.
These problems occur also in extreme conditions on the ground, for example, in a vacuum, where it is difficult to use oil or grease as a lubricant.